A.R.S. § 13-3889: Method of arrest by private person

A private person when making an arrest shall inform the person to be arrested of the intention to arrest him and the cause of the arrest, unless he is then engaged in the commission of an offense, or is pursued immediately after its commission or after an escape, or flees or forcibly resists before the person making the arrest has opportunity so to inform him, or when the giving of such information will imperil the arrest.